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Avoid laying a refrigerator on its side. The oil in the compressor can flow into the cooling lines when the refrigerator is tipped onto its side. When returned to an upright position, there is a risk that the oil will not completely drain from the cooling lines and the refrigerator will not cool.
If you have to lay the fridge over, try to avoid laying it completely flat. Instead tip it to an angle by placing a box under the top of the fridge; this will help to keep the oil in the compressor. Also, there are several lines connected to the compressor. The cooling and discharge lines should be oriented to face up. You must keep the oil out of these lines. Laying the refrigerator over with the tubes facing up will minimize the risk of fouling the lines.
When you have the refrigerator in place at its destination, leave it upright for a few hours before plugging it in. This will give the oil an opportunity to flow back into the compressor. After plugging it in, it is not unusual for the fridge to take up to 72 hours to return to its low temperatures, especially if the fridge is empty.
If after all your effort the refrigerator won't cool, your refrigerator may be in its defrost cycle, so be patient, about 6 hours, for the cycle to complete. Otherwise, there may be oil in the lines. In that case, you will need professional repair.